Light source unit and projector

ABSTRACT

A light source unit of the present invention includes a first light source and a second light source that are configure to emit light in a first wavelength range, a luminescent plate configured to be excited by the light in a first wavelength range to emit light in a second wavelength range, and a dichroic filter provided on one surface side of the luminescent plate and configured to transmit the light in a second wavelength, and the light in a first wavelength range emitted from the first light source is incident on the dichroic filter at an angle within a first incident angle range, and the light in a first wavelength range emitted from the second light source is incident on the dichroic filter at an angle within a second incident angle range that is greater than the first incident angle range.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of prior U.S. application Ser. No.16/560,801, filed on Sep. 4, 2019, which claims the benefit of JapanesePatent Application No. 2018-186676 filed on Oct. 1, 2018, the entiredisclosure of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a light source unit and a projectorincluding the light source unit.

Description of the Related Art

In these days, projectors are used in which light emitted from a lightsource is collected onto a micromirror display device called a digitalmicromirror device (DMD) or a liquid crystal panel so as to display acolor image onto a screen.

For example, Japanese Patent Laid-Open No. 2012-212129(JP-A-2012-212129) discloses a light source unit that includes anexcitation light source made up of a laser light source, a first wheelprovided with a luminescent material layer excited by excitation lightemitted from the excitation light source and configured to reflectluminescent light emitted from the luminescent material layer, and adichroic mirror provided between the first wheel and the excitationlight source and configured to guide luminescent light and excitationlight to an illuminating optical system. The first wheel is divided intoa plurality of segments, and at least one segment reflects excitationlight, while a luminescent material layer emitting light having awavelength in the red, yellow or green wavelength range is provided onat least two segments. Additionally, a quarter wave plate changing thepolarization direction is disposed between the first wheel and thedichroic mirror.

In the light source unit disclosed in JP-A-2012-212129, since excitationlight emitted from the excitation light source is shined on to the firstwheel, which is rotating, to emit light having a wavelength in the bluewavelength range, light having a wavelength in the red wavelength rangeand light having a wavelength range in the green wavelength range in atime sharing manner, it is difficult to reduce the size of the lightsource further.

SUMMARY OF THE INVENTION

The present invention has been made in view of the situations describedabove, and an object of the present invention is to provide a lightsource unit whose configuration is simplified and a projector includingthe light source unit.

According to an aspect of the present invention, there is provided alight source unit including:

a first light source and a second light source that are configure toemit light in a first wavelength range;

a luminescent plate configured to be excited by the light in a firstwavelength range to emit light in a second wavelength range; and

a dichroic filter provided on one surface side of the luminescent plateand configured to transmit the light in a second wavelength,

wherein the light in a first wavelength range emitted from the firstlight source is incident on the dichroic filter at an angle within afirst incident angle range, and

wherein the light in a first wavelength range emitted from the secondlight source is incident on the dichroic filter at an angle within asecond incident angle range that is greater than the first incidentangle range.

According to another aspect of the present invention, there is provideda projector including:

the light source unit described above;

a display device on to which light source light from the light sourceunit is shined to form image light;

a projection optical system configured to project the image lightemitted from the display device on to a screen; and

a control unit configured to control the display device and the lightsource unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating functional circuit blocks of aprojector according to a first embodiment of the present invention;

FIG. 2 is a schematic plan view illustrating an internal structure ofthe projector according to the first embodiment of the presentinvention;

FIG. 3 is a partially plan schematic view of a light source unitaccording to the first embodiment of the present invention;

FIG. 4A is a diagram illustrating a transmission characteristic of lightincident on a dichroic filter according to the first embodiment of thepresent invention at a first incident angle;

FIG. 4B is a diagram illustrating a transmission characteristic of lightincident on the dichroic filter according to the first embodiment of thepresent invention at a second incident angle; and

FIG. 5 is a partially plan schematic view of a light source unitaccording to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

Hereinafter, a first embodiment of the present invention will bedescribed. FIG. 1 is a block diagram illustrating functional circuitblocks of a projector 10. A projector control unit includes a CPUincluding an image transforming module 23 and a controller 38, and afront-end unit including an input/output interface 22, and a formatterunit including a display encoder 24 and a display driver 26. Imagesignals of various standards which are inputted from an input/outputconnector unit 21 are sent, via the input/output interface 22 and asystem bus (SB), to the image transforming module 23, where the imagesignals are transformed so as to be unified into an image signal of apredetermined format which is suitable for display. Thereafter, theunified image signal to the display encoder 24.

The display encoder 24 deploys the inputted image signal on a video RAM25 for storage in it and generates a video signal from the contentsstored in the video RAM 25, outputting the video signal so generated tothe display driver 26.

The display driver 26 functions as a display device controller. Thedisplay driver 26 drives a display device 51, which is a spatial opticalmodulator (SOM), at an appropriate frame rate according to the imagesignal outputted from the display encoder 24. Then, in the projector 10,pencils of light emitted from a light source unit 60 are shined on tothe display device 51 by way of a light guiding optical system tothereby form an optical image by light reflected from the display device51, and the image so formed is then projected onto a screen, notillustrated, for display by way of a projection optical system, whichwill be described later. A movable lens group 235 of the projectionoptical system is driven by a lens motor 45 for zooming and focusing.

An image compression/expansion unit 31 performs a recording process inwhich a luminance signal and a color difference signal of an imagesignal are data compressed through processing of Adaptive DiscreteCosine Transform (ADCT) and Huffman coding, and the compressed data issequentially written on a memory card 32, which constitutes a detachablerecording medium. Further, with the projector 10 set in a reproducingmode, the image compression/expansion unit 31 reads out the image datarecorded in the memory card 32 and expands the individual image datathat makes up a series of dynamic images frame by frame. Then, the imagecompression/expansion unit 31 outputs the image data to the displayencoder 24 by way of the image transforming module 23 and enables thedisplay of dynamic images based on the image data stored in the memorycard 32.

The controller 38 governs the control of operations of individualcircuitries inside the projector 10 and includes CPU, ROM storingfixedly operation programs such as various settings, RAM that is used asa work memory, and the like.

Operation signals from a keys/indicators unit 37 including main keys andindicators which are provided on an upper panel of a casing of theprojector 10 are sent out directly to the controller 38. Key operationsignals from a remote controller are received by an IR reception unit 35and are then demodulated into a code signal at an Ir processing unit 36for output to the controller 38.

The controller 38 is connected with an audio processing unit 47 by wayof a system bus (SB). This audio processing unit 47 includes a circuitryfor a sound source such as a PCM sound source. With the projector 10 setin a projection mode and the reproducing mode, the audio processing unit47 converts audio data into analog signals and drives a speaker 48 tooutput loudly sound or voice based on the audio data.

The controller 38 controls a light source control circuit 41, whichfunctions as a light source control unit. The light source controlcircuit 41 controls individually operations of an excitation lightshining device 70, a green light source device 80, and a red lightsource device 120 (refer to FIG. 2) of the light source unit 60 so thatlight in predetermined wavelength ranges required in generating an imageis emitted from the light source unit 60.

Further, the controller 38 causes a cooling fan drive control circuit 43to detect temperatures with a plurality of temperature sensors which areprovided in the light source unit 60 so as to control revolution speedsof cooling fans based on the results of the temperature detections.Additionally, the controller 38 also causes the cooling fan drivecontrol circuit 43 to keep the cooling fans revolving by use of a timeror the like even after a power supply to a main body of the projector 10is switched off. Alternatively, the controller 38 causes the cooling fandrive control circuit 43 to cut off the power supply to the main body ofthe projector 10 depending upon the results of the temperaturedetections by the temperature sensors.

FIG. 2 is a schematic plan view illustrating an internal structure ofthe projector 10. It should be noted that in the following description,when left and right are referred to in relation to the projector 10,they denote, respectively, left and right directions with reference to aprojecting direction of the projector 10. When front and rear arereferred to in relation to the projector 10, they denote, respectively,front and rear directions with reference to a direction from theprojector 10 towards a screen and a traveling direction of a pencil oflight from the projector 10.

The projector 10 includes a control circuit board 241 in the vicinity ofa left panel 15. This control circuit board 241 includes a power supplycircuit block, a light source control block, and the like. The projector10 also includes the light source unit 60 at a substantially centralportion of the casing of the projector 10. Further, the projector 10includes a light source-side optical system 170 and a projection opticalsystem 220 that are disposed between the light source unit 60 and theleft panel 15.

The light source unit 60 includes the excitation light shining device70, which constitutes not only a light source of light of a wavelengthin the blue wavelength range or, simply, light in the blue wavelengthrange (light in a first wavelength range) but also an excitation lightsource, a green light source device 80, which constitutes a light sourceof light of a wavelength in the green wavelength range or, simply, lightin the green wavelength range (light in a second wavelength range), thered light source device 120, which constitutes a light source of lightof a wavelength in the red wavelength range or, simply, light in the redwavelength range (light in a third wavelength range), and a lightguiding optical system 140.

The excitation light shining device 70 is disposed at a substantiallycentral portion of the casing of the projector 10 in a left-rightdirection. The excitation light shining device 70 includes a lightsource group made up of blue laser diodes 71 (blue laser diodes 711, 712which constitute a first light source, and blue laser diodes 713 whichconstitute a second light source) that are a plurality of semiconductorlight emitting elements disposed in such a manner that optical axesthereof are parallel to a right panel 14 and the left panel 15, and aheat sink 81 disposed between the blue laser diodes 71 and a front panel12, and the like.

The light source group is formed by arranging the plurality of laserdiodes 71 into a matrix configuration. In this embodiment, assuming thata left-right direction in FIG. 2 is referred to as a row and a directionperpendicular to a surface of a sheet of paper on which FIG. 2 is drawnis referred to as a column, a total of 10 blue laser diodes is arrangedinto a matrix configuration of two rows and five columns in a side viewas viewed from a rear panel 13. In a plan view of the projector 10, acolumn of blue laser diodes 711 (71) is positioned at a center of theexcitation light shining device 70, and columns of blue laser diodes 712(71) are positioned on both sides of the column of blue laser diodes 711(71). Columns of blue laser diodes 713 (71) are positioned individuallyon outer sides of the corresponding columns of blue laser diodes 712(71). Light beams L1 to L3 in the blue wavelength range are emitted fromthe blue laser diodes 71 towards a polarization beam splitter 141 as apolarized light of s-polarized light.

A plurality of collimator lenses 73 are disposed individually on opticalaxes of the blue laser diodes 71 so as to convert light emitted from thecorresponding blue laser diodes 71 into parallel light to therebyenhance the directivity of the emitted light. The collimator lenses 73are disposed in such a manner as to deviate towards the central columnof blue laser diodes 711 in the matrix of blue laser diodes 71.Additionally, a deviation amount of the collimator lenses 73 is made tobecome greater as the collimator lenses 73 lie farther away from thecentral column of blue laser diodes 711. The blue laser diodes 71 areformed into the two rows in FIG. 2, and the collimator lenses 73disposed for the blue laser diodes 711, 712, 713 in an upper row arealso disposed in such a manner as to slightly deviate downwards. Thus,the light beams L2, L3 in the blue wavelength range emitted from theouter blue laser diodes 712, 713 can be collected towards the light beamL1 in the blue wavelength range by disposing the collimator lenses 73 insuch a manner as to be eccentric inwards in the way described above,whereby an effective diameter of an optical member such as a collectivelens group 111 can be reduced.

A power supply connector 57 and a heat sink 150 are disposedsequentially in this order as seen from the rear panel 13 between thelight source unit 60 and the right panel 14. In addition, the lightsource unit 60 includes a heat pipe 130 configured to guide heatgenerated in the excitation light shining device 70 to the heat sink 150and a cooling fan 261 configured to cool the heat sink 150. The bluelaser diodes 71 are cooled by this cooling fan 261, the heat pipe 130,and the heat sinks 81, 150.

The green light source device 80 is made up of the excitation lightshining device 70 and a luminescent light emitting device 100. Asillustrated in FIG. 3, the luminescent light emitting device 100includes a luminescent plate 101, a dichroic filter 102, a quarter waveplate 103, and the collective lens group 111. The luminescent plate 101,the dichroic filter 102, and the quarter wave plate 103 are formedintegrally. The collective lens group 111 collects pencils of excitationlight emitted from the excitation light shining device 70 towards theluminescent light emitting device 100 and also collects pencils of lightemitted from the luminescent light emitting device 100 towards thepolarization beam splitter 141.

The luminescent plate 101 is disposed in such a manner as to intersectan axis of light emitted from the excitation light shining device 70 andguided via the polarization beam splitter 141 at right angles. Theluminescent plate 101 includes a base material in which a surface on aside facing the dichroic filter 102 is mirror finished through silverdeposition or the like to constitute a reflecting surface and a greenluminescent material formed on the base material. When light in the bluewavelength range emitted from the excitation light shining device 70 isshined on to the luminescent plate 101, the luminescent plate 101 emitslight in the green wavelength range as luminescent light. Since thesurface of the base material of the luminescent plate 101 is mirrorfinished to constitute the reflecting surface, the light in the greenwavelength range is reflected towards the collective lens group 111. Thebase material can be formed of metal such as copper, aluminum, or thelike. Alternatively, the luminescent plate 101 may be formed of asintered luminescent material containing a luminescent material and aninorganic binder, and in this case, no base material needs to beprovided.

The dichroic filter 102 is formed on the luminescent plate 101 throughcoating. Here, referring to FIGS. 4A, 4B, transmission characteristicsof the dichroic filter 102 will be described. FIG. 4A shows transmissioncharacteristics Ts1, Tp1 when light is incident on the dichroic filter102 at a first incident angle θ1, which is a relatively small incidentangle. The transmission characteristic Ts1 denotes a characteristic oflight when s-polarized light is incident on the dichroic filter 102,while the transmission characteristic Tp1 denotes a characteristic oflight when p-polarized light is incident on the dichroic filter 102. Thefirst incident angle θ1 can be, for example, almost 0 degree or 15degrees. In the case where the first incident angle θ1 is 0 degree,cuton wavelengths of the transmission characteristics Ts1, Tp1 aresubstantially the same in FIG. 4. In the case where the first incidentangle θ1 is 15 degrees, the cuton wavelengths of the transmissioncharacteristics Ts1, Tp1 are close to each other in FIG. 4. In thesecases, the transmission characteristics Ts1, Tp1 are situated closer toa long wavelength side than peak wavelengths of the light rays L1, L2 inthe blue wavelength range emitted from the blue laser diodes 711.Additionally, the dichroic filter 102 reflects light shined in awavelength range closer to a short wavelength side where thetransmittance of the transmission characteristics Ts1, Tp1 issubstantially 0%. Consequently, the dichroic filter 102 can reflect mostof s-polarized light and p-polarized light in the blue wavelength rangethat are incident on the dichroic filter 102 at the first incident angleθ1.

Although the light beam L2 in the blue wavelength range is incident onthe dichroic filter 102 at a greater incident angle than the light beamL1 in the blue wavelength range as illustrated in FIG. 3, as with thelight beam L1 in the blue wavelength range illustrated in FIG. 4A, cutonwavelengths of transmission characteristics Ts1, Tp1 are situated closerto a long wavelength side than a peak wavelength of the light beam L2 inthe blue wavelength range, and most of the light beam L2 in the bluewavelength range is reflected by the dichroic filter 102. In this way,the light beams L1, L2 in the blue wavelength range emitted from theblue laser diodes 711, 712 are incident on the dichroic filter 102 atthe first incident angle θ1 that falls in the range where light incidenton the dichroic filter 102 can be reflected by the dichroic filter 102.

FIG. 4B shows transmission characteristics Ts2, Tp2 when light isincident on the dichroic filter 102 at a second incident angle θ2, whichis greater than the first incident angle θ1. The transmissioncharacteristic Ts2 denotes a characteristic of light when s-polarizedlight is incident on the dichroic filter 102, while the transmissioncharacteristic Tp2 denotes a characteristic of light when p-polarizedlight is incident on the dichroic filter 102. The second incident angleθ2 can be, for example, 45 degree or 65 degrees. In the case where theincident angle is the second incident angle θ2, cuton wavelengths of thetransmission characteristics Ts2, Tp2 shift further towards a short waveside than the transmission characteristics Ts1, Tp1 shown in FIG. 4A. Inaddition, the case where the incident angle is the second incident angleθ2, the cuton wavelength of the transmission characteristic Tp2 and thecuton wavelength of the transmission characteristic Ts2 is spaced apartmore than the transmission characteristics Ts1, Tp1 when the incidentangle is the first incident angle θ1. However, both the cuton wavelengthof the transmission characteristic Ts2 and the cuton wavelength of thetransmission characteristic Tp2 are situated closer to the shortwavelength side than a peak wavelength of the light beam L3 in the bluewavelength range emitted by the blue laser diodes 713. Thus, thedichroic filter 102 can transmit most of s-polarized light andp-polarized light in the blue wavelength range that are incident on thedichroic filter 102 at the second incident angle θ2. In this way, thelight beam L3 in the blue wavelength range emitted from the blue laserdiodes 713 is incident on the dichroic filter 102 at the second incidentangle θ2 that falls in the range where light incident on the dichroicfilter 102 can be transmitted by the dichroic filter 102.

In this way, the dichroic filter 102 is formed so that the cutonwavelengths of the transmission characteristics Ts1, Tp1 are situated onthe long wavelength side of light in the blue wavelength range when theincident angle of light is the first incident angle θ1 (FIG. 4A) , whilethe cuton wavelengths are situated on the short wavelength side of lightin the blue wavelength range when the incident angle of light is thesecond incident angle θ2 that is greater than the first incident angle(FIG. 4B) . That is, the light beams L1, L2 in the blue wavelength range(light in a first wavelength range) emitted from the blue laser diodes711, 711A, 712, 712A (71, 71A) (a first light source) are incident onthe dichroic filter 102 at an angle that falls within the first incidentangle range including the first incident angle θ1, while the light beamL3 in the blue wavelength range (light in a first wavelength range)emitted from the blue laser diodes 713, 713A (71, 71A) (a second lightsource) is incident on the dichroic filter 102 at an angle that fallswithin the second incident angle range including the second incidentangle θ2 that is greater than the first incident angle θ1.

Returning to FIG. 3, the quarter wave plate 103 is formed on thedichroic filter 102. The quarter wave plate 103 can shift light in theblue wavelength range emitted from the excitation light shining device70 and then shined through the collective lens group 111 in phase 90degrees. Consequently, the light beams L1 to L3 in the blue wavelengthrange, which are linearly polarized light, are converted into linearlypolarized light whose polarization direction differs 90 degrees fromthat of the original linearly polarized light by double passing thequarter wave plate 103.

As shown in FIG. 2, the red light source device 120 includes a red lightemitting diode 121 (a third light source) disposed in such a manner thatan optical axis thereof becomes substantially parallel to optical axesof the blue laser diodes 71 and a collective lens group 125 configuredto collect light emitted from the red light emitting diode 121. The redlight emitting diode 121 is a semiconductor light element that emitslight in the red wavelength range.

The light guiding optical system 140 includes the polarization beamsplitter 141 and a dichroic mirror 142. The polarization beam splitter141 is disposed between the collective lens group 111 and the dichroicmirror 142 and is disposed on a side of the excitation light shiningdevice 70 that faces the rear panel 13. The polarization beam splitter141 can separate or split polarization components. The polarization beamsplitter 141 reflects s-polarized light in the blue wavelength range andtransmits p-polarized light in the blue wavelength range, thepolarization direction of the p-polarized light being different 90degrees from that of the s-polarized light. Consequently, thepolarization beam splitter 141 reflects s-polarized light in the bluewavelength range emitted from the excitation light emitting device 70towards the luminescent light emitting device 100 and transmitsp-polarized light in the blue wavelength range emitted from theluminescent light emitting device 100. The polarization beam splitter141 transmits light in the green wavelength range emitted from theluminescent light emitting device 100 towards the dichroic mirror 142.

The dichroic mirror 142 is disposed on an axis of light in the redwavelength range emitted from the red light source device 120 andbetween the polarization beam splitter 141 and a collective lens 173.The dichroic mirror 142 reflects light in the red wavelength rangeemitted from the red light source device 120 to the collective lens 173.Additionally, the dichroic mirror 142 guides and transmits light in theblue wavelength range and light in the green wavelength range that areemitted from the polarization beam splitter 141 to the collective lens173.

Here, an optical path of light in the blue wavelength range emitted fromthe excitation light shining device 70 will be described. Light beamsL1, L2 in the blue wavelength range emitted from the blue laser diodes711, 712 shown in FIG. 3 are incident on the polarization beam splitter141 in the form of s-polarized light and are then reflected towards thecollective lens 111 by the polarization beam splitter 141. The lightbeams L1, L2 are collected by the collective lens group 111, thereafter,are caused to shift in phase 90 degrees by the quarter wave plate 103 tobe converted from linearly polarized light to circularly polarizedlight, and are incident on the dichroic filter 102. Since the lightbeams L1, L2 in the blue wavelength range are incident on the dichroicfilter 102 at the first incident angle θ1, which is relatively small,most of the light beams L1, L2 are reflected on the dichroic filter 102as indicated by the transmission characteristics Ts1, Tp1 in FIG. 4A.

The light beams L1, L2 in the blue wavelength range reflected by thedichroic film 102 pass the quarter wave plate 103 again, whereby thelight beams L1, L2 are caused to shift in phase another 90 degrees,whereby the light beams L1, L2 are converted from circularly polarizedlight into linearly polarized light. A polarization direction (a secondpolarization direction) at this time differs 90 degrees from thepolarization direction (a first polarization direction) in which thelight beams L1, L2 are incident on the luminescent light emitting device100 from the polarization beam splitter 141. In this embodiment, thefirst polarization direction is the direction of s-polarized lightrelative to the polarization beam splitter 141, and the secondpolarization direction is the direction of p-polarized light relative tothe polarization beam splitter 141. The light beams L1, L2 in the bluewavelength range emitted from the quarter wave plate are collected bythe collective lens group 111 and are then incident on the polarizationbeam splitter 141 in the form of p-polarized light. Consequently, thepolarization beam splitter 141 transmits the light beams L1, L2 in theblue wavelength range emitted from the luminescent light emitting device100 and guides them to the dichroic mirror 142.

Since the blue laser diodes 713 are configured to be arranged sidewayswith respect to the blue laser diodes 711, 712, light beams L3 emittedfrom the blue laser diodes 713 arrive at the dichroic filter 102 by wayof the same optical member (the polarization beam splitter 141 and thecollective lens group 111 in FIG. 3) as that by way of which the lightbeams L1, L2 emitted from the blue laser diodes 711, 712 arrive.

The light beams L3 emitted from the blue laser diodes 713 shown in FIG.3 are incident on the polarization beam splitter 141 in the form ofs-polarized light and are then reflected towards the collective lensgroup 111 by the polarization beam splitter 141. The light beams L3 inthe blue wavelength range are collected by the collective lens group111, thereafter, are caused to shift in phase 90 degrees by the quarterwave plate 103 to thereby be converted from linearly polarized light tocircularly polarized light, and are incident on the dichroic filter 102.Since the light beams L3 in the blue wavelength range are incident onthe dichroic filter 102 at the second incident angle θ2, which isgreater than the first incident angle θ1, most of the light beams L3 areallowed to pass through the dichroic filter 102 as indicated by thetransmission characteristics Ts2, Tp2 in FIG. 4B.

The light beams L3 in the blue wavelength range pass through thedichroic filter 102 and are then incident on the luminescent plate 101to excite the green luminescent material formed on the luminescent plate101. When the light beams L3 in the blue wavelength range are shined onto the green luminescent material, the green luminescent material emitsrandomly polarized light in the green wavelength range in everydirection. Since the base material of the luminescent plate 101 ismirror finished, light in the green wavelength range emitted towards theluminescent plate 101 is reflected towards the collective lens group111.

Light in the green wavelength range emitted from the luminescent plate101 is incident on the dichroic mirror 142. Since light in the greenwavelength range is light having a longer wavelength than that of lightin the blue wavelength range, light in the green wavelength range canpass through the dichroic mirror 102. Thus, the dichroic mirror 102transmits light in the green wavelength range emitted from theluminescent plate 101, causing it to be incident on the quarter waveplate 103. Thereafter, the light in the green wavelength range passesthrough the quarter wave plate 103 while being shifted in phase 90degrees and is then collected by the collective lens group 111,whereafter the light in the green wavelength range is emitted towardsthe polarization beam splitter 141. The polarization beam splitter 141transmits the light in the green wavelength range collected at thecollective lens group 111 and guides it to the dichroic mirror 142.

The excitation light shining device 70 can switch emission of excitationlight by the blue laser diodes 71 thereof between emission of lightbeams L1, L2 in the blue wavelength range by the blue laser diodes 711,712 so as to be incident on the dichroic filter 102 at the firstincident angle θ1 and emission of light beams L3 in the blue wavelengthrange by the blue laser diodes 713 so as to be incident on the dichroicfilter 102 at the second incident angle θ2 in a time-sharing manner. Asa result, the light source unit 60 can emit light in the blue wavelengthrange and light in the green wavelength range from the luminescent lightemitting device 100 by switching the emission of light therefrom betweenthe emission of light in the blue wavelength range and the emission oflight in the green wavelength range in a time-sharing manner.

The light source-side optical system 170 includes the collective lens173, a light guiding device 175 such as a light tunnel, a glass rod, orthe like, collective lenses 178, 179, a light shining mirror 185, and acondenser lens 195. The condenser lens 195 emits image light emittedfrom the display device 51 that is disposed on a side of the condenserlens 195 that faces the rear panel 13 towards the projection opticalsystem 220, and hence, the condenser lens 195 also makes up part of theprojection optical system 220.

The collective lens 173 is disposed near an incident port of the lightguiding device 175 and collects light source light from the light sourceunit 60. Light beams in the blue, red, and green wavelength rangesemitted from the light source unit 60 are collected by the collectivelens 173 and are then emitted towards the light guiding device 175. Apencil of light emerging from an emerging port of the light guidingdevice 175 is collected at the collective lenses 178, 179 and is thenguided towards the light shining mirror 185.

The light shining mirror 185 reflects the pencil of light collected atthe collective lenses 178, 179 and shines it on the display device 51 ata predetermined angle via the condenser lens 195. The display device 51,which takes the form of DMD, is provided on a side of a heat sink 190that faces the rear panel 13, whereby the display device 51 is cooled bythis heat sink 190.

The pencil of light, which is the light source light shined on to animage forming surface of the display device 51 by the light source-sideoptical system 170, is reflected on the image forming surface of thedisplay device 51 and is then projected on to a screen by way of theprojection optical system 220 as projected light. Here, the projectionoptical system 220 is made up of the condenser lens 195, the movablelens group 235, and a fixed lens group 225. The movable lens group 235is configured to be moved by the lens motor or manually. In addition,the movable lens group 235 and the fixed lens group 225 are incorporatedin a fixed lens barrel. Thus, the fixed lens barrel including themovable lens group 235 is configured as a variable-focus lens enablingzooming and focusing controls.

By configuring the projector 10 in the way that has been describedheretofore, when light is emitted from the excitation light shiningdevice 70 and the red light source device 120 at appropriate timings,light in the blue wavelength range, light in the green wavelength range,and light in the red wavelength range are incident on the display device51 by way of the light guiding optical system 140 and the lightsource-side optical system 170. Due to this, the display device 51,which takes the form of DMD, of the projector 10 displays light in eachof the blue, green and red wavelength ranges in accordance with the datain the time-sharing manner, whereby a colored image can be projected onto the screen.

Second Embodiment

Next, a second embodiment will be described. FIG. 5 is a schematic planview illustrating part of a light source unit 60 according to the secondembodiment. In this embodiment, blue laser diodes 711A, 712A (a firstlight source) configured to emit light beams L1, L2 in the bluewavelength range in such a manner as to be incident on a dichroic filter102 at a first incident angle θ1 and blue laser diodes 713A (a secondlight source) configured to emit light beams L3 in the blue wavelengthrange in such a manner as to be incident on the dichroic filter 102 at asecond incident angle θ2 are not arranged side by side or into a matrixof rows and columns. In the description of the second embodiment, likereference signs will be given to like configurations to those of thefirst embodiment, and descriptions thereof will be omitted or simplifiedhere.

Light beams L1, L2 in the blue wavelength range emitted from the bluelaser diodes 711A, 712A travel along a similar optical path to that ofthe first embodiment. In other words, light beams L1, L2 in the bluewavelength range emitted by the blue laser diodes 711A, 712A areincident on a polarization beam splitter 141 as s-polarized light andare then reflected towards a collective lens group 111 by thepolarization beam splitter 141. The light beams L1, L2 in the bluewavelength range are collected at the collective lens group 111,thereafter are shifted in phase 90 degrees by a quarter wave plate 103to thereby be converted from linearly polarized light to circularlypolarized light, and are finally incident on the dichroic filter 102.Since the light beams L1, L2 in the blue wavelength range are incidenton the dichroic filter 102 at the first incident angle θ1, most of themare reflected at the dichroic filter 102.

The light beams L1, L2 in the blue wavelength range reflected by thedichroic filter 102 pass again through the quarter wave plate 103 to beshifted in phase another 90 degrees to thereby be converted from thecircularly polarized light to linearly polarized light. A polarizationdirection at this time constitutes a polarization direction (a secondpolarization direction) that differs 90 degrees from a polarizationdirection (a first polarization direction) in which the light beams L1,L2 in the blue wavelength range are incident on a luminescent lightemitting device 100 from the polarization beam splitter 141. The lightbeams L1, L2 in the blue wavelength range emitted from the quarter waveplate 103 are collected at the collective lens group 111 and are thenincident on the polarization beam splitter 141 as p-polarized light.Consequently, the polarization beam splitter 141 transmits the lightbeams L1, L2 in the blue wavelength range emitted from the luminescentlight emitting device 100 and guides them to the dichroic mirror 142.

On the other hand, the blue laser diodes 713A are not arranged on thesame plane or straight line as that of the blue laser diodes 711A, 712Abut are arranged in different positions from the blue laser diodes 711A,712A. The blue laser diodes 711A, 712A and the blue laser diodes 713Aemit light beams L1 to L3 in the blue wavelength range in differentdirections. Light beams L3 in the blue wavelength range emitted from theblue laser diodes 713A arrive at the dichroic filter 102 by way of asmaller number of optical members (in FIG. 5, excluding the polarizationbeam splitter 141 and the collective lens group 111) than the number ofoptical members by way of which the light beams L1, L2 in the bluewavelength range emitted from the blue laser diodes 711A, 712A arrivethereat. As a result, the blue laser diodes 713A can cause light beamsL3 in the blue wavelength range to be directly incident on theluminescent light emitting device 100 without involving the polarizationbeam splitter 141 and the collective lens group 111, whereby it becomeseasier to set the second incident angle θ2 greater than in the firstembodiment. In the case where the second incident angle θ2 is setgreater than in the first embodiment, the transmission characteristicsTp2, Ts2 shown in FIG. 4B shift further towards the short wavelengthside, facilitating the transmission of light beams L3 in the bluewavelength through the dichroic filter 102. Light beams L3 in the bluewavelength range emitted from the blue laser diodes 713A are emittedtowards the dichroic filter 102 as p-polarized light or s-polarizedlight.

Similar to the first embodiment, the light beams L3 in the bluewavelength range that have passed through the dichroic filter 102 areincident on a luminescent plate 101 to excite a green luminescentmaterial formed on the luminescent plate 101.

Light in the green wavelength range emitted from the luminescent plate101 is incident on the dichroic filter 102. Since light in the greenwavelength range is light having a longer wavelength than light in theblue wavelength range, light in the green wavelength range passesthrough the dichroic filter 102 to be incident on the quarter waveplate. Thereafter, the light in the green wavelength range passesthrough the quarter wave plate while being shifted in phase 90 degrees,is collected by the collective lens group 111 and is then emittedtowards the polarization beam splitter 141. The polarization beamsplitter 141 transmits the light in the green wavelength range collectedat the collective lens group 111 and guides it to a dichroic mirror 142.

Thus, in the configuration of the second embodiment that has beendescribed heretofore, since the blue laser diodes 711A, 712A areprovided separate from the blue laser diodes 713A, the incident angle atwhich the light beams L3 in the blue wavelength range, configured toexcite the green luminescent material, are incident on the dichroicfilter 102 can be set greater. This enables the reflection ortransmission of light beams L1 to L3 in the blue wavelength range of thesame color system at the dichroic filter 102 to be controlled easily,thereby making it possible to improve the color repeatability of lightin the green wavelength range and light in the blue wavelength rangethat are emitted from the luminescent light emitting device 100.

Although the luminescent light emitting device 100 is described as beingthe integral member, part or the whole of the luminescent plate 101, thedichroic filter 102 and the quarter wave plate 103 may be formed asseparate elements.

The blue laser diodes 711 to 713 of the first embodiment and the bluelaser diodes 711A to 713A of the second embodiment may be disposedopposite to the luminescent light emitting device 100 so that lightbeams in the blue wavelength range emitted from those blue laser diodesare guided to the luminescent light emitting device 100. In this case,the light source unit 60 can be configured so that light in the bluewavelength range and light in the green wavelength range that areemitted from the luminescent light emitting device 100 are reflected onthe polarization beam splitter 141 to be guided to the dichroic mirror142 that is arranged appropriately on the optical path. The dichroicmirror 142 may be configured to reflect the light in the blue wavelengthrange and light in the green wavelength range that are guided theretofrom the polarization beam splitter 140 and transmit light in the redwavelength range emitted from the red light source device 120, wherebythe light in the blue wavelength range, the light in the greenwavelength range, and the light in the red wavelength range are combinedtogether to be guided to the light source-side optical system 170.

In the embodiments, although the polarization beam splitter 141 isdescribed as reflecting light in the form of s-polarized light andtransmitting light in the form of p-polarized light, the polarizationbeam splitter may be configured to reflect light in the form ofp-polarized light and transmit light in the form of s-polarized light.

Thus, as has been described heretofore, the light source unit 60 and theprojector 10 include the first light source and the second light sourcethat are configured to emit light in the first wavelength range, theluminescent plate 101 configured to be excited by light in the firstwavelength range to emit light in the second wavelength range, and thedichroic filter 102 provided on the one surface side of the luminescentplate 101 and configured to transmit light in the second wavelengthrange. Light in the first wavelength range emitted from the first lightsource is incident on the dichroic filer 102 at the angle falling in thefirst incident angle range, and light in the first wavelength rangeemitted from the second light source is incident on the dichroic filter102 at the angle falling within the second incident angle range that isgreater than the first incident angle range.

As a result, although the first light source and the second light sourceconstitute the light sources that emit light in the same wavelengthrange, the first light source and the second light source can bedisposed in the different positions, whereby the first light source andthe second light source can emit light that is reflected by the dichroicfilter 102 and light that passes through the dichroic filter 102. Inaddition, the luminescent plate 101 can emit light in the bluewavelength range and light in the green wavelength range in thetime-sharing manner without switching the area where light in the firstwavelength range emitted from the first light source and the secondlight source is shined in the time-sharing manner. Thus, the lightsource unit 60 and the projector 10 that are simplified in configurationcan be provided.

The light source unit 60 includes the polarization beam splitter 141 andthe quarter wave plate 103. The polarization beam splitter 141 reflectsor transmits light in the first wavelength range and in the firstpolarization direction emitted from the first light source and thesecond light source towards the dichroic filter 102 and transmits orreflects light in the first wavelength range and in the secondpolarization direction that differs in phase 90 degrees from the firstpolarization direction towards the dichroic filter 102. The quarter waveplate 103 is disposed between the polarization beam splitter 141 and thedichroic filter 102. As a result of the configuration described above,light in the first wavelength range emitted from the dichroic filter 102can be guided for use in the different direction from the direction inwhich light from the first light source and the second light source isguided.

In the light source unit 60, the dichroic filter 102 is formed on theluminescent plate 101, and the quarter wave plate 103 is formed on thedichroic filter 102. Thus, in the light source unit 60, the opticalmember including the dichroic filter 102 and the quarter wave plate 103can be formed small.

The light source unit 60 includes the third light source and thedichroic mirror 142. The third light source emits light in the thirdwavelength range that differs from the wavelength ranges of light in thefirst wavelength range and light in the second wavelength range. Thedichroic mirror 142 transmits or reflects light in the first wavelengthrange and light in the second wavelength range emitted from thepolarization beam splitter 141 and reflects or transmits light in thethird wavelength range emitted from the third light source. As a result,in the light source unit 60, light in the third wavelength range can becombined with light in the first wavelength range and light in thesecond wavelength range on the same optical path to be guided as lightsource light.

The light source unit 60 can emit light in the first wavelength rangeand light in the second wavelength range in the time-sharing manner, andhence, the light source unit 60 can emit light in the first wavelengthrange and light in the second wavelength range emerging from thedichroic filter 102 in the time-sharing manner.

The light source unit 60 includes the dichroic filter 102 configured sothat when the incident angle of light incident thereof is the firstincident angle θ1, the cuton wavelength ranges of the transmissioncharacteristics Ts1, Tp1, Ts2, Tp2 are situated on the long wavelengthside of the light in the first wavelength range, whereas when theincident angle of light incident thereof is the second incident angle θ2that is greater than the first incident angle θ1, the cuton wavelengthranges are situated on the short wavelength side of the light in thefirst wavelength range. Thus, with the light source unit 60, the lightin the first wavelength range can easily be shined onto the luminescentplate 101 by increasing the incident angle of the light in the firstwavelength range.

In addition, the second light source is provided side by side with thefirst light source, and light in the first wavelength range emitted fromthe second light source arrives at the dichroic filter 102 by way of theoptical members such as the polarization beam splitter 141 and thecollective lens group 111 by way of which light in the first wavelengthrange emitted from the first light source arrives at the dichroic filter102. Due to this, the first light source and the second light source canbe incorporated into the same holding member by laying the first lightsource and the second light source adjacent to each other, whereby thefirst light source and the second light source can be disposed in asmall exclusive space with good efficiency.

In addition, the second light source is disposed in the differentposition from the position where the first light source is disposed, andlight in the first wavelength range emitted from the second light sourcearrives at the dichroic filter 102 by way of a smaller number of opticalmembers than the number of optical members by way of which light in thefirst wavelength range emitted from the first light source arrives atthe dichroic filter 102. Due to this, the degree of freedom inarrangement of the second light source can be improved in an attempt,for example, to increase the second incident angle θ2.

The first light source and the second light source are the blue laserdiodes for emitting light beams L1 to L3 in the blue wavelength range aslight in the first wavelength range. Due to this, not only can light inthe blue wavelength range be emitted as light source light, but alsolight in the green wavelength range which is situated closer to the longwavelength side than light in the blue wavelength range can be emittedas luminescent light from the luminescent plate 101.

In the embodiment described above, a color wheel (not shown) can beprovided directly before an incident surface of the light guiding device175 that is positioned on the optical path of light emitted from theblue laser diodes 711 (71) to 713 (71) of the excitation light shiningdevice 70.

The color wheel is made up of three segments. These three segments are adiffuse transmission zone configured to transmit light in the bluewavelength range while diffusing it, a red transmission zone configuredto transmit light in the red wavelength range, and a green selectionfilter configured to reflect or absorb light in the blue wavelengthrange that is not used for excitation of the green luminescent materialon the luminescent plate 101 in transmitting light in the greenwavelength range. These three segments are provided end to end in acircumferential direction at predetermined angular intervals. Inaddition, the color wheel can rotate around a rotational axis that isparallel to an optical axis direction by the controller and rotates insuch a manner as to match timings at which light in each of the blue,green, red wavelength ranges is emitted in the time-sharing manner.

In the embodiments, the dichroic mirror 142 is described as beingprovided to reflect light in the red wavelength range emitted from thered light source device 120 towards the collective lens 173, but thepresent invention is not limited to this configuration. The red lightsource device 120 may be disposed so that the polarization beam splitter141 is positioned on an axis of light in the red wavelength rangeemitted from the red light source device 120. In this case, a reflectionfilm configured to reflect only light in the red wavelength range isformed on a surface of the polarization beam splitter 141 on to whichlight in the red wavelength range emitted from the red light sourcedevice 120 is shined. Since the dichroic mirror 142 can be eliminated bythis configuration, the light source unit 60 can be miniaturized.

While the embodiments and modified examples of the present inventionhave been described heretofore, the embodiments and the modifiedexamples are presented as examples, and hence, there is no intention tolimit the scope of the present invention by these embodiments andmodified examples. These novel embodiments can be carried out in othervarious forms, and various omissions, replacements and modifications canbe made to the embodiments without departing from the spirit and scopeof the present invention. Those resulting embodiments and theirmodifications are included in the spirit and scope of the presentinvention and are also included in the scope of inventions claimed forpatent under claims below and their equivalents.

What is claimed is:
 1. A light source unit comprising: a luminescentplate configured to be excited by light in a first wavelength range toemit light in a second wavelength range; a dichroic filter provided onone surface side of the luminescent plate; a first light source that isconfigured to emit light in the first wavelength range to the surface ofthe dichroic filter opposite to the luminescent plate side; and a secondlight source that is arranged at a position different from the firstlight source and emits the light in the first wavelength range to thesurface of the dichroic filter opposite to the luminescent plate side,wherein the first light source is arranged so as to emit the light inthe first wavelength range to the dichroic filter at a first incidentangle such that a reflectance of the light in the first wavelength rangeis larger than a transmittance of the light in the first wavelengthrange, and wherein the second light source is arranged so as to emit thelight in the first wavelength range to the dichroic filter at a secondincident angle such that a transmittance of the light in the firstwavelength range is larger than a reflectance of the light in the firstwavelength range.
 2. The light source unit according to claim 1,comprising: a polarization beam splitter configured to reflect ortransmit the light in the first wavelength range in a first polarizationdirection emitted from the first light source to the dichroic filter andto transmit or reflect the light in the first wavelength in a secondpolarization that differs in phase 90 degrees from the firstpolarization direction; and a quarter wave plate disposed between thepolarization beam splitter and the dichroic filter.
 3. The light sourceunit according to claim 2, wherein the quarter wave plate is formed onthe dichroic filter.
 4. The light source unit according to claim 2,comprising: a third light source configured to emit light in a thirdwavelength range that differs from wavelength ranges of the light in thefirst wavelength range and the light in the second wavelength range. 5.The light source unit according to claim 4, comprising: a dichroicmirror configured to transmit or reflect the light in the firstwavelength range and the light in the second wavelength range emittedfrom the polarization beam splitter and to reflect or transmit the lightin the third wavelength range emitted from the third light source. 6.The light source unit according to claim 1, wherein the dichroic filteris formed so that when an incident angle of the light in the firstwavelength range falls within the first incident angle, a cutonwavelength of a transmission characteristic is situated on a longwavelength side of the light in a first wavelength range, whereas whenan incident angle of the light in the first wavelength range fallswithin the second incident angle that is greater than the first incidentangle, the cuton wavelength is situated on a short wavelength side ofthe light in the first wavelength range.
 7. The light source unitaccording to claim 1, wherein the second light source is provided sothat at least a part of the light in the first wavelength range emittedfrom the second light source transmits the dichroic filter and arrivesat the luminescent plate.
 8. The light source unit according to claim 1,wherein the first light source is provided so that a portion of thelight in the first wavelength range emitted from the first light sourcethat is reflected by the dichroic filter is directed toward a collectivelens, and wherein the second light source is provided so that the lightin the first wavelength range emitted from the second light sourcearrives at the luminescent plate, and the light in the second wavelengthrange emitted by the excitation of the luminescent plate is directedtoward the collective lens.
 9. The light source unit according to claim1, wherein the second light source is provided side by side with thefirst light source, and wherein the light in the first wavelength rangeemitted from the second light source arrives at the dichroic filter byway of a same optical member as an optical member by which the light inthe first wavelength range emitted from the first light source arrivesat the dichroic filter.
 10. The light source unit according to claim 1,wherein the light in the first wavelength range emitted from the secondlight source arrives at the dichroic filter by way of a smaller numberof optical members than a number of optical members byway of which thelight in the first wavelength range emitted from the first light sourcearrives at the dichroic filter.
 11. The light source unit according toclaim 2, wherein the light in the first wavelength range emitted fromthe second light source arrives at the dichroic filter by way of asmaller number of optical members than a number of optical members bywayof which the light in the first wavelength range emitted from the firstlight source arrives at the dichroic filter.
 12. The light source unitaccording to claim 1, wherein the first light source and the secondlight source are a blue laser diode that emits light in a bluewavelength range as the light in the first wavelength range.
 13. Aprojector comprising: the light source according to claim 1; a displaydevice on to which light source light from the light source unit isshined to form image light; a projection-side optical system configuredto project the image light emitted from the display device on to ascreen; and a control unit configured to control the display device andthe light source unit.